Active Noise Control Ear Cup with Dual Feedforward ANC
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Solution Overview
Problem
Conventional active noise control systems in head-worn purifiers struggle to effectively attenuate both external environmental and internally originating noise, such as the noise generated by a fan within the ear cup, as they are not designed to handle both exogenous and endogenous noise sources simultaneously.
Innovation Solution
The ear cup incorporates a housing with a filter assembly, a motor-driven impeller, an acoustic driver, a reference internal noise sensor, and active noise control circuitry that uses both a reference internal noise sensor and a reference ambient noise sensor to generate anti-noise signals, combining them with the desired audio signal to optimize noise cancellation. This includes an inner feedforward ANC system to address endogenous noise and an outer feedforward ANC system for exogenous noise, potentially switching between them based on noise levels for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional active noise control systems are used in head-worn purifiers, then external environmental noise can be attenuated, but internally originating noise (endogenous noise) from the fan cannot be effectively cancelled
Solution Approach 1:
The patent divides the noise control system into two separate feedforward ANC systems: an outer feedforward ANC system for handling external environmental noise and an inner feedforward ANC system for handling internal fan noise. Each system has its own reference noise sensor positioned to detect specific noise sources, allowing independent optimization of noise cancellation for each type without interference.
Solution Approach 2:
The patent introduces reference noise sensors as intermediary elements that detect noise before it reaches the user's ear. The outer reference noise sensor detects external environmental noise, while the inner reference noise sensor detects internal fan noise. These sensors serve as mediators that provide early noise information to the respective ANC systems for proactive cancellation.
2Device complexity
If a single feedforward ANC system is used, then system complexity is reduced, but the ability to simultaneously cancel both external and internal noise is compromised
Solution Approach 1:
The patent segments the single ANC system into two independent feedforward ANC subsystems, each dedicated to a specific noise source. This segmentation allows each subsystem to be optimized for its specific function while maintaining relative simplicity in individual system design.
Solution Approach 2:
The patent creates a multi-functional ANC system where two feedforward ANC systems operate simultaneously within the same ear cup housing. The outer feedforward ANC system handles external noise while the inner feedforward ANC system handles internal noise, providing universal noise cancellation capability across different noise sources.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly improves noise attenuation by simultaneously addressing both external and internal noise sources, providing enhanced noise cancellation performance while maintaining social acceptability and ease of use.
Implementation Method 1
Active noise control uses destructive interference to attenuate noise. The frequency, amplitude and phase of any undesired sound are identified and another sound of the same frequency and amplitude but opposite phase is created, i.e. an 'anti-noise' sound, with the intention that this 'anti-noise' sound will cancel out the noise.
Implementation Method 2
a reference internal noise sensor and active noise control circuitry that uses both a signal provided by the reference internal noise sensor and a signal provided by a reference ambient noise sensor
Data Source
AI summary
There is provided an ear cup including a housing containing a filter assembly and a motor-driven impeller for creating an airflow through the filter assembly, the housing including an air outlet downstream from the filter assembly for emitting the filtered airflow from the housing. The ear cup further includes an acoustic driver mounted to the housing, a reference internal noise disposed within the housing and a reference ambient noise mounted to the housing. The ear cup further includes active noise control circuitry that is configured to simultaneously use both a signal provided by the reference internal noise and the signal provided by the reference ambient noise to operate the acoustic driver.